HSC Survey Results

Scots Bay Survey # 4 Results from 16/06/2024

Survey Details

6 commercial purse seiners conducted this fishing survey on 16/06/2024 starting at 20:00:00, which was 0.52 hours before hide tide.

All vessels ran two transects each in the Main Survey Box, the Canada 100 ran four lines in the Eastern Survey Box, and the Leroy and Barry ran four lines in the Northern Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 33,846mt, and with turnover applied 22,278mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-06-16 19:38 2024-06-16 22:30 -65.233 45.073 -64.727 45.240 SB 43.90 8.27
BP T02 2024-06-16 22:51 2024-06-17 0:59 -64.794 45.287 -65.227 45.137 SB 37.91 9.60
C1 T01 2024-06-16 19:51 2024-06-16 20:44 -64.705 45.222 -64.555 45.264 SB 13.04 7.97
C1 T02 2024-06-16 20:52 2024-06-16 21:47 -64.551 45.285 -64.713 45.239 SB 13.98 8.24
C1 T03 2024-06-16 21:55 2024-06-16 22:58 -64.733 45.256 -64.554 45.304 SB 15.48 7.96
C1 T04 2024-06-16 23:12 2024-06-17 0:22 -64.553 45.327 -64.771 45.267 SB 18.77 8.69
FM T01 2024-06-16 20:56 2024-06-16 23:39 -65.226 45.089 -64.743 45.252 SB 42.25 8.40
FM T02 2024-06-17 0:02 2024-06-17 2:09 -64.812 45.297 -65.234 45.150 SB 37.17 9.48
LB T01 2024-06-16 19:43 2024-06-16 20:40 -65.048 45.290 -64.884 45.340 SB 14.22 8.08
LB T02 2024-06-16 20:47 2024-06-16 21:48 -64.867 45.332 -65.050 45.276 SB 15.74 8.36
LB T03 2024-06-16 21:57 2024-06-16 23:05 -65.043 45.265 -64.849 45.325 SB 16.81 8.01
LB T04 2024-06-16 23:12 2024-06-17 0:21 -64.834 45.316 -65.051 45.250 SB 18.61 8.74
LJ T01 2024-06-16 19:44 2024-06-16 22:47 -65.235 45.054 -64.703 45.229 SB 46.34 8.20
LJ T02 2024-06-16 23:11 2024-06-17 1:36 -64.775 45.276 -65.234 45.119 SB 40.11 8.96
LM T01 2024-06-16 19:35 2024-06-16 22:24 -65.239 45.100 -64.756 45.265 SB 42.57 8.16
LM T02 2024-06-16 22:44 2024-06-17 0:57 -64.827 45.309 -65.231 45.167 SB 36.14 8.80

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
FM T02 -35.5 -39.465 0.401
LJ T02 -35.5 -50.406 0.032
FM T01 -35.5 -51.062 0.028
LM T01 -35.5 -52.234 0.021
BP T01 -35.5 -52.347 0.021
LM T02 -35.5 -53.707 0.015
LJ T01 -35.5 -54.152 0.014
LB T04 -35.5 -58.178 0.005
LB T03 -35.5 -60.760 0.003
C1 T04 -35.5 -61.292 0.003
LB T02 -35.5 -61.302 0.003
C1 T01 -35.5 -62.038 0.002
C1 T03 -35.5 -62.120 0.002
BP T02 -35.5 -64.905 0.001
LB T01 -35.5 -65.205 0.001
C1 T02 -35.5 -65.290 0.001
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 533 -47.5367 0.0667 33,323.0454 72.0 98.5 25,527.16 76.61
Northern Box -35.5 85 -60.4922 0.0030 270.1238 11.5 0.8 76.31 28.25
Eastern Box -35.5 122 -62.3418 0.0020 252.6191 16.5 0.7 41.47 16.42

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by FM, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by FM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856.000 40,856 0 0
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767.329 108,783 NA NA
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279.387 15,158 NA NA
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,744.776 5,113 NA NA
Scots Bay 5 NA NA NA 2023-07-16 19,282.634 17,575 NA NA
Scots Bay 6 NA NA NA 2023-07-30 4,549.933 1,904 NA NA
Scots Bay 7 NA NA NA 2023-08-13 4,298.806 3,616 NA NA
Scots Bay 9 NA NA NA 2023-09-10 3,053.669 2,916 NA NA
Scots Bay 10 NA NA NA 2023-09-24 3,419.932 2,997 NA NA
Scots Bay 8 NA NA NA 2023-08-27 2,896.659 2,300 NA NA
Scots Bay 11 NA NA NA 2023-10-09 3,387.515 2,971 NA NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,536.6 204,189 NA NA
2024 Scots Bay 235,655.0 207,718 NA NA

Plankton, and CTD Data

Summary map

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number SB2024-07 SB2024-08
Ground SB SB
Date 16/06/2024 16/06/2024
Wind Direction (km/h) W W
Swell (m) 0.5 0.5
Air Temp (c) 21 21
Tow Details
Tow Start 18:37:00 18:53:00
Tow End 18:47:00 19:03:00
Start Lat 45.05200 45.05167
End Lat 45.1005 45.0545
Start Lon -65.21933 -65.20850
End Lon -65.20967 -65.21083
Avg Tow Depth (m) 11.1680189 0.4472721
Speed 3.7 1.6
Heading 37 192
Tide Direction with against
Other Data Collection
Flow Start 982880 7845
Flow End 7845 40725
No. Revolutions -975035 32880
Distance (m) -26202.1156 883.5842
Volume -82313.95 2775.78
Secchi Disappear (m) 9 9
Secchi Reappear (m) 8 8

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-07, which was with the tide and had an average depth of 11.1680189m. The second tow is SB2024-08, which was against the tide and had an average depth of 0.4472721m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.57. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

More than 2km of distance was cut from the planned lines; vessels are reminded to complete their assigned lines straight and without deviating or cutting corners short.